Here's my code:

#include <cstdio>
using namespace std;


unsigned long long int a,b,c,d,s,h;


int main() {

    //Read Data
    scanf("%d%d%d%d",&a,&b,&c,&d);

    //Calculate
    s=c-a;
    s/=b+d;
    a+=s*b;
    c-=s*d;
    if (c-a>=b) a+=b;

    //Write Data
    printf("%d\n",a);


    //End
    return 0;
}

2 1 1 1
Answer 2.

it works correctly