Go: package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"strings"
)

func main() {
	io := NewIo()
	defer io.Flush()
	a, b, c := io.NextInt(), io.NextInt(), io.NextInt()
	for i := 0; i < 61; i++ {
		for j := 0; j < 61; j++ {
			if (a+b)*i-60*j <= c && c <= (a+b)*i-60*j+a {
				io.Println(60*j + c)
				return
			}
		}
	}
	io.Println(-1)
}

// I/O template
type Io struct {
	reader    *bufio.Reader
	writer    *bufio.Writer
	tokens    []string
	nextToken int
}

func NewIo() *Io {
	return &Io{
		reader: bufio.NewReader(os.Stdin),
		writer: bufio.NewWriter(os.Stdout),
	}
}

func (io *Io) Flush() {
	err := io.writer.Flush()
	if err != nil {
		panic(err)
	}
}

func (io *Io) NextLine() string {
	var buff []byte
	for {
		line, isPrefix, err := io.reader.ReadLine()
		if err != nil {
			panic(err)
		}
		buff = append(buff, line...)
		if !isPrefix {
			break
		}
	}
	return string(buff)
}

func (io *Io) Next() string {
	for io.nextToken >= len(io.tokens) {
		line := io.NextLine()
		io.tokens = strings.Fields(line)
		io.nextToken = 0
	}
	s := io.tokens[io.nextToken]
	io.nextToken++
	return s
}

func (io *Io) NextInt() int {
	i, err := strconv.Atoi(io.Next())
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) NextFloat() float64 {
	i, err := strconv.ParseFloat(io.Next(), 64)
	if err != nil {
		panic(err)
	}
	return i
}

func (io *Io) Println(a ...interface{}) {
	fmt.Fprintln(io.writer, a...)
}

func (io *Io) Printf(format string, a ...interface{}) {
	fmt.Fprintf(io.writer, format, a...)
}

func (io *Io) PrintIntSlice(a []int) {
	b := make([]interface{}, 0, len(a))
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func (io *Io) PrintStringSlice(a []string) {
	b := make([]interface{}, 0, len(a))
	for _, x := range a {
		b = append(b, x)
	}
	io.Println(b...)
}

func Log(name string, value interface{}) {
	fmt.Fprintf(os.Stderr, "%s=%+v\n", name, value)
}

func ExampleIo() {
	io := NewIo()
	defer io.Flush()
	a := make([]int, 0, 3)
	a[0], a[1], a[2] = io.NextInt(), io.NextInt(), io.NextInt()
	io.Println(a)
	io.PrintIntSlice(a)
	Log("io", a)
}

C++: #include <iostream>
#include <cstdio>
#include <string>
#include <vector>
#include <algorithm>
#include <cmath>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>
#include <stack>
#include <queue>
//ranker
using namespace std;

#define REPS(i, a, n) for (int i = (a); i < (n); ++i)
#define REP(i, n) REPS(i, 0, n)
#define RREP(i, n) REPS(i, 1, n + 1)
#define DEPS(i, a, n) for (int i = (a); i >= n; --i)
#define DEP(i, n) DEPS(i, n, 0)

using ll = long long;
using ull = unsigned long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vvvi = vector<vvi>;
using pii = pair<int, int>;
using pis = pair<int, string>;
using psi = pair<string, int>;
using D = double;

void merge (int *first1, int *last1, int *first2, int *last2){
    int size1 = last1 - first1;
    int size2 = last2 - first2;
    int *result = new int[size1+size2];
    int i = 0;
    int j = 0;
    int index = 0;
    while (true){
        if (i < size1 && (first1[i] <= first2[j] || j >= size2)){
            result[index] = first1[i];
            ++i; ++index;
        }
        if (j < size2 && (first1[i] > first2[j] || i >= size1)){
            result[index] = first2[j];
            ++j; ++index;
        }
        if (i==size1 && j==size2){
            for (i=0; i<size1; ++i) first1[i] = result[i];
            for (j=0; j<size2; ++j) first2[j] = result[j+size1];
            delete[] result;
            return;
        }
    }
}
void MergeSort (int *first, int *last){
    int size = last - first;
    if(size <= 1) return;
    MergeSort(first, first+size/2);
    MergeSort(first+size/2, last);
    merge(first, first+size/2, first+size/2, last);
}

//?????°????????????
void sort2vectors(vector<int> &av, vector<int> &bv)
{
        int n = av.size();
        vector<int> p(n), av2(n), bv2(n);
        iota(p.begin(), p.end(), 0);
        sort(p.begin(), p.end(), [&](int a, int b) { return av[a] < av[b]; });
        for (int i = 0; i < n; i++) {
                av2[i] = av[p[i]];
                bv2[i] = bv[p[i]];
        }
        av = av2;
        bv = bv2;
}


int gcd(int a, int b)
{
    int c;
    if (a < b) {
        a+=b; b=a-b; a-=b;
    }
    while (b != 0) {
        c = a % b;
        a = b;
        b = c;
    }
    return a;
}

int isPrime(int x){
  int i;
  if(x < 2) return 0;
  else if(x == 2) return 1;
  if( x%2 == 0) return 0;
  for(i = 3; i*i <= 2; i += 2){
    if(x%i == 0) return 0;
  }
  return 1;
}


const int pmax = 10000000;
bool isPrime_table[pmax];
//const???????????¨????????£?¨???§?????????

void eratos(void){
  int i, j;
  double sqrtmax=sqrt(pmax);

  REP(k, pmax) isPrime_table[k] = true; /* Initialization */

  /* Sieve process  */
  isPrime_table[0] = false;
  isPrime_table[1] = false;
          /* 0 and 1 are not prime. */
  for (i=2; i <= sqrtmax; i++){
    if (isPrime_table[i]==true){   /* i is prime. */
      for (j=i; i*j<pmax; j++){
        isPrime_table[i*j] = false; /* multiples of i are not prime. */
      }
    }
  }
}

//????????????????¨???°?????????
//abs(dx[i]+dy[j])==1??§??????
int dx[3]={-1, 0, 1};
int dy[3]={-1, 0, 1};
int W0, H0;
int  masu0[100][100]={0};
int cnt0;

int dfs(int a, int b){
  masu0[a][b] = 2;
  REP(i, 3)REP(j, 3){
    a = a+dx[i];
    b = b+dy[j];
    if(masu0[a][b]== 1 && a >= 0 && a < W0 && b >= 0 && b < H0){
    dfs(a, b);
  }
  }
  return 1;
}

//????????????????????????str.substr(i, 5)
//????????°????????? stoi, stod ??¨to_string
//?????????memset
//?????°??????????????????
//dp
const string abet("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ");

int main(void){
  cin.tie(0);
  ios::sync_with_stdio(false);

  int a, b, c;
  cin >> a >> b >> c;

  if(a + b == 60){
    if(a >= c) cout << c << endl;
    else cout << -1 << endl;
  }else{
    int cnt = 0;
    while(((a+b)*cnt)%60+a < c || c <= ((a+b)*cnt)%60){
      cnt++;
    }
    cout << cnt << endl;
    cout << (a+b)*cnt + c-((a+b)*cnt)%60 << endl;
  }
  return 0;
}

C++: #include<iostream>
#include<map>
#include<vector>
#include<algorithm>
#include<cmath>
#include<climits>
#include<ctime>
#include<cstring>
#include<numeric>

#define ALL(v) (v).begin(),(v).end()
#define REP(i,p,n) for(int i=p;i<(int)(n);++i)
#define rep(i,n) REP(i,0,n)
#define dump(a) (cerr << #a << "=" << (a) << endl)
#define DUMP(list) cout << "{ "; for(auto nth : list){ cout << nth << " "; } cout << "}" << endl;

using namespace std;

int main() {
	int A, B, C;
	cin >> A >> B >> C;
	int time = 0;	
	if(A >= C || (C % (A+B)) <= A) { // ティツオツキテ」ツ?催」ツ?ヲテ」ツ??」ツつ凝ゥツ鳴禿」ツ?ォテァツ敖?」ツ??
		time = C;
	} 
	else if(60 % (A+B) == 0 || C % (A+B) == 0) { // ティツセツソテ」ツつ甘」ツ?、テ」ツ?妥」ツ?ェテ」ツ??・ツ?エテ・ツ青?
		time = -1;
	}
	else { // テ・ツ堕ィテ・ツ崢榲」ツ?凖」ツつ凝・ツ?エテ・ツ青?
		for(int i = 0; time < C; ++i) {
			time += (i % 2 == 0) ? A : B;
		}
		int k  = time - C; // ティツカツ?ゥツ?偲・ツ按?
		int t = C / k; // テ・ツ堕ィテ・ツ崢榲ヲツ閉ー
		time = 60*t + C;
	}
	cout << time << endl;	
	return 0;
}

C++: #include<cstdio>

int main(void) {
    int a,b,c;
    scanf("%d%d%d",&a,&b,&c);
    for(int i=0; i<10000; i++) {
        int test=60*i+c;
        if( test%(a+b) <= a ) {
            printf("%d\n",test);
            return 0;
        }
    }
    printf("-1\n");
    return 0;
}

C++: def solve(a, b, c):
    l = 0; r = a;
    for t in range(114514):
        t = l // 60
        p = 60*t + c
        if l <= p <= r:
            print(p)
            exit()

        l = r + b
        r = l + a

    print(-1)

a, b, c = map(int, input().split())
solve(a,b,c)