C++ :

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <cstdlib>
#include <iostream>
using namespace std;

int main()
{
  //freopen("in.txt", "r", stdin);
  //freopen("out.txt", "w", stdout);
  int a, b, x, y;
  while(scanf("%d%d%d%d", &a, &b, &x, &y) != EOF)
  {
    int ans = 100 + a * x - b * y;
    if(ans <= 0)
      printf("0\n");
    else
      printf("%d\n", ans);
  }
  return 0;
}