CodeForces 652A Gabriel and Caterpillar

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

int h1,h2;
int a,b;

int main()
{
scanf("%d%d",&h1,&h2);
scanf("%d%d",&a,&b);
if(h1+8*a>=h2) printf("0\n");
else if(h1+8*a<h2&&b>=a) printf("-1\n");
else
{
h1=h1+8*a;
int ans=0;
while(1)
{
ans++;
h1=h1-12*b;
h1=h1+12*a;
if(h1>=h2) break;
}
printf("%d\n",ans);
}
return 0;
}