#include<stdio.h>

int main(){
    int p, d, s, m, count = 0, sum = 0;
    
    scanf("%d %d %d %d",&p ,&d, &m, &s);
    
    while( sum < s ){
         sum = sum + p;
         if( sum <= s )
            count++;  
         p = p - d;
         if( p<=m )
            p = m;
            
    }

    printf("%d\n",count);
    
    return 0;
}