C++ :

#include <iostream>
#include <string>
using namespace std;
int main()
{
    int n,m,l;
    string s,s1;
    while(cin>>n>>m)
    {
        cin>>s;
        l=s.size();
        s.replace(n,m,"GLAG");
        cout<<s<<endl;
    }
    return 0;
}