Language: C++

#include <climits>
#define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define srep(i, begin, end) for (__typeof(end) i = begin; i != end; i++)
#define si(x) int x = scanInt();
#define sll(x) LL x = scanLong();
#define sci(x) int x; scanf("%d", &x);
#define scll(x) LL x; scanf("%lld", &x);
#define pi(x) printf("%d ", x)
#define pll(x) printf("%lld ", x)
#define nl printf("\n")
#define clr(a) memset(a, 0, sizeof(a))
#define PB push_back
#define MP make_pair
using namespace std;
typedef unsigned int UI; // 32 bit integer
typedef long int LI; // 32 bit integer
typedef unsigned long int ULI; // 32 bit unsigned integer
typedef long long int LL; // 64 bit integer
typedef unsigned long long int ULL; // 64 bit unsigned integer
typedef long double LD;
typedef vector<int> VI;
typedef vector<LL> VLL;
typedef deque<int> DI;
typedef deque<LL> DLL;
typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;
const LL MOD = 1e9+7;

/* Fast I/O */
inline int scanInt() {
	int n = 0;
	char ch = getchar();
	int sign = 1;
	while(ch < '0' || ch > '9') {
		if(ch == '-')	sign = -1;
		ch = getchar();
	}
	while(ch >= '0' && ch <= '9') {
		n = (n<<1)+(n<<3)+(int)(ch-'0');
		ch = getchar();
	}
	return n*sign;
}

inline LL scanLong() {
	LL n = 0;
	char ch = getchar();
	LL sign = 1;
	while(ch < '0' || ch > '9') {
		if(ch == '-')	sign = -1;
		ch = getchar();
	}
	while(ch >= '0' && ch <= '9') {
		n = (n<<1)+(n<<3)+(LL)(ch-'0');
		ch = getchar();
	}
	return n*sign;
}

int main() {
	sll(n); sll(k);
	string str; cin >> str;
	str[k-1] += ('a' - 'A');
	cout << str << endl;
}


Compiler output:
a.cc:21:9: error: 'vector' does not name a type
   21 | typedef vector<int> VI;
      |         ^~~~~~
a.cc:22:9: error: 'vector' does not name a type
   22 | typedef vector<LL> VLL;
      |         ^~~~~~
a.cc:23:9: error: 'deque' does not name a type
   23 | typedef deque<int> DI;
      |         ^~~~~
a.cc:24:9: error: 'deque' does not name a type
   24 | typedef deque<LL> DLL;
      |         ^~~~~
a.cc:25:9: error: 'pair' does not name a type; did you mean 'pi'?
   25 | typedef pair<int, int> PII;
      |         ^~~~
      |         pi
a.cc:26:9: error: 'pair' does not name a type; did you mean 'pi'?
   26 | typedef pair<LL, LL> PLL;
      |         ^~~~
      |         pi
a.cc: In function 'int scanInt()':
a.cc:32:19: error: 'getchar' was not declared in this scope
   32 |         char ch = getchar();
      |                   ^~~~~~~
a.cc:2:1: note: 'getchar' is defined in header '<cstdio>'; this is probably fixable by adding '#include <cstdio>'
    1 | #include <climits>
  +++ |+#include <cstdio>
    2 | #define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
a.cc: In function 'LL scanLong()':
a.cc:47:19: error: 'getchar' was not declared in this scope
   47 |         char ch = getchar();
      |                   ^~~~~~~
a.cc:47:19: note: 'getchar' is defined in header '<cstdio>'; this is probably fixable by adding '#include <cstdio>'
a.cc: In function 'int main()':
a.cc:62:9: error: 'string' was not declared in this scope
   62 |         string str; cin >> str;
      |         ^~~~~~
a.cc:2:1: note: 'std::string' is defined in header '<string>'; this is probably fixable by adding '#include <string>'
    1 | #include <climits>
  +++ |+#include <string>
    2 | #define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
a.cc:62:21: error: 'cin' was not declared in this scope
   62 |         string str; cin >> str;
      |                     ^~~
a.cc:2:1: note: 'std::cin' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
    1 | #include <climits>
  +++ |+#include <iostream>
    2 | #define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
a.cc:62:28: error: 'str' was not declared in this scope; did you mean 'std'?
   62 |         string str; cin >> str;
      |                            ^~~
      |                            std
a.cc:64:9: error: 'cout' was not declared in this scope
   64 |         cout << str << endl;
      |         ^~~~
a.cc:64:9: note: 'std::cout' is defined in header '<iostream>'; this is probably fixable by adding '#include <iostream>'
a.cc:64:24: error: 'endl' was not declared in this scope
   64 |         cout << str << endl;
      |                        ^~~~
a.cc:2:1: note: 'std::endl' is defined in header '<ostream>'; this is probably fixable by adding '#include <ostream>'
    1 | #include <climits>
  +++ |+#include <ostream>
    2 | #define rep(i, begin, end) for (__typeof(end) i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))