Problem:
Score : 300 points

Problem Statement

You are given an integer N.

For two positive integers A and B, we will define F(A,B) as the larger of the following: the number of digits in the decimal notation of A, and the number of digits in the decimal notation of B.

For example, F(3,11) = 2 since 3 has one digit and 11 has two digits.

Find the minimum value of F(A,B) as (A,B) ranges over all pairs of positive integers such that N = A \times B.

Constraints

1 \leq N \leq 10^{10}

N is an integer.

Input

The input is given from Standard Input in the following format:

N

Output

Print the minimum value of F(A,B) as (A,B) ranges over all pairs of positive integers such that N = A \times B.

Sample Input 1

10000

Sample Output 1

3

F(A,B) has a minimum value of 3 at (A,B)=(100,100).

Sample Input 2

1000003

Sample Output 2

7

There are two pairs (A,B) that satisfy the condition: (1,1000003) and (1000003,1). For these pairs, F(1,1000003)=F(1000003,1)=7.

Sample Input 3

9876543210

Sample Output 3

6

Solution in C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <stdlib.h>
#include <stdbool.h>
#define MOD 1000000007
#define END printf("\n");return 0;
void input_array(int how_data,int *data);
void input_array2(int first , int second , int data[][2]);
int get_random(int min, int max);
int factorial(int n);
int fibonacci(int n);
int qsort_09(const int *sys1 , const int *sys2);
int qsort_90(const int *sys1 , const int *sys2);
long sel_max(long a , long b);
int sel_min(int a , int b);
int array_max(int how_data,int *data);
int array_min(int how_data,int *data);
int can_DP(int how_data,int *data,int how_can,bool *can);
int array_sum(int how_data,int *data);
int Leven_dist(char *now , char *target);
void prime_fact(long target, int *data);
int loop1,loop2,loop3,loop4,loop5,i_temp;
char c_temp;

int main(void){
    long n;
    scanf("%ld",&n);
    int prime[25]={0};
    prime_fact(n,prime);
    loop1=25-1;
    long tempA=1;
    long tempB=1;
    while(loop1>=0){
        if(prime[loop1]!=0){
            //printf("%d\n",loop1);
            //printf("%d\n",prime[loop1]);
            if(tempA<tempB){
                tempA*=prime[loop1];
            }else{
                tempB*=prime[loop1];
            }
        }
        loop1--;
    }
    //printf("%ld %ld\n",tempA,tempB);
    long temp=sel_max(tempA,tempB);
    printf("%ld\n",(long)log10(temp)+1);
    
    return 0;
}


//how_data個の配列data[]に標準入力
//input_array(how_data,data);
void input_array(int how_data,int *data){
    int loop;
    for(loop=0;loop<how_data;loop++){
        scanf("%d",&data[loop]);
    }
    return ;
}

void input_array2(int first,int second,int data[][2]){
    int loopA,loopB;
    for(loopA=0;loopA<first;loopA++){
        for(loopB=0;loopB<second;loopB++){
            scanf("%d",&data[loopA][loopB]);
        }
    }
    return ;
}

int get_random(int min, int max){   //指定の範囲から乱数を1つ返すやつ
    //srand((unsigned int)time(0));   //現在時刻で疑似乱数初期化
    rand();rand();rand();rand();    //乱数を空打ち
    return (rand()%(max+1-min))+min;
}


int factorial(int n){//n!のMOD10^9+7を返すやつ
    unsigned long long int ret=1;
    for(int i=1;i<=n;i++)ret=(ret*i)%1000000007;
    return (int)ret;
}

int qsort_09(const int *sys1 , const int *sys2){ //小さいのが上にくるやつ
    //qsort(data,how_data,sizeof(int),(int (*)(const void *,const void *))qsort_09);
    if(*sys1<*sys2){
        return -1;
    }else if(*sys1==*sys2){
        return 0;
    }else{
        return 1;
    }
}

int qsort_90(const int *sys1 , const int *sys2){ //大きいのが上にくるやつ
    //qsort(data,how_data,sizeof(int),(int (*)(const void *,const void *))qsort_90);
    if(*sys1<*sys2){
        return 1;
    }else if(*sys1==*sys2){
        return 0;
    }else{
        return -1;
    }
}

int fibonacci(int n){
    switch(n){
        case 0:return 0;
        case 1:return 1;
        default :return fibonacci(n-1)+fibonacci(n-2);
    }
}

long sel_max(long a,long b){
    if(a>b)return a;
    return b;
}

int sel_min(int a,int b){
    if(a>b)return b;
    return a;
}

int can_DP(int how_data,int *data,int how_can,bool *can){//Typical DP Contest A
    //data内で組み合わせられる和をcanに0 or 1で入れる
    //返り値はパターン数
    int loopA,loopB;
    int ret=0;
    for(loopA=0;loopA<how_can;loopA++){//初期化
        can[loopA]=0;
    }
    can[0]=1;//絶対にありえる
    for(loopA=0;loopA<how_data;loopA++){
        for(loopB=how_can-1;loopB>=0;loopB--){
            if(can[loopB]==1 && loopB+data[loopA]<how_can){
                can[loopB+data[loopA]]=1;
            }
        }
    }
    for(loopA=0;loopA<how_can;loopA++){
        if(can[loopA]==1){
            ret++;
        }
    }
    return ret;
}
int array_max(int how_data,int *data){
    int loop;
    int ret=data[0];
    for(loop=0;loop<how_data;loop++){
        if(ret<data[loop])ret=data[loop];
    }
    return ret;
}
int array_min(int how_data,int *data){
    int loop;
    int ret=data[0];
    for(loop=0;loop<how_data;loop++){
        if(ret>data[loop])ret=data[loop];
    }
    return ret;
}
int array_sum(int how_data,int *data){
    int ret=0;
    int loop;
    for(loop=0;loop<how_data;loop++){
        ret+=data[loop];
    }
    return ret;
}
int Leven_dist(char *now , char *target){
    int loopA,loopB;
    //レーベンシュタイン距離を求める
    // 参考文献
    // http://nw.tsuda.ac.jp/class/algoB/c13.html  (アルゴリズム理解)
    // http://d.hatena.ne.jp/ohnishiakira/20090809/1249845529  (実装)
    int len_now=strlen(now)+1;
    int len_target=strlen(target)+1;
    int d[len_now][len_target]; //計算用
    for(loopA=0;loopA<len_now;loopA++) d[loopA][0]=loopA;
    for(loopA=0;loopA<len_target;loopA++) d[0][loopA]=loopA;
    for(loopA=1;loopA<len_now;loopA++){
        for(loopB=1;loopB<len_target;loopB++){
            int cost=(now[loopA-1]==target[loopB-1] ? 0:1);
            d[loopA][loopB]=sel_min(sel_min(d[loopA-1][loopB]+1,d[loopA][loopB-1]+1),d[loopA-1][loopB-1]+cost);
        }
    }
    return d[len_now-1][len_target-1];
}
void prime_fact(long target, int *data){
    int loopB=0;
    int loopA=2;
    while(target!=1){
        loopA-=1;
        while(1){
            loopA++;
            if(loopA>=100000){
                data[loopB]=target;
                target=1;
                break;
            }
            if(target%loopA==0){
                data[loopB]=loopA;
                target/=loopA;
                loopB++;
                break;
            }
        }
    }
    return ;
}