Không có test mẫu, :/ ác 

Code :

#include <bits/stdc++.h>
#define int long long
using namespace std;
signed main(){
    int a,b,m;
    cin>>a>>b>>m;
    int diff=a-b;
    cout<<(m+diff-1)/diff;
}

#include<iostream>
using namespace std;
long long a,b,m;
int main() {
    cin>>a;
    cin>>b;
    cin>>m;
    long long kq=abs(m-b);
    long long n=kq/abs(a-b);
    if (a>=m)
     cout<<1;
    else 
            if (kq%abs(a-b)==0) cout<<kq%abs(a-b);
    else 
            cout<<kq%abs(a-b)+1;
    return 0;
}