80分求各位大佬调

#include<bits/stdc++.h>
using namespace std;
int main()
{
	int m,t,s;
	cin>>m>>t>>s;
    if(!(m>1)) cout<<"0";
    else if(!(t>1)) cout<<"0";
    else if(!(s>=1)) cout<<"0";
	else if(m>1&&t>1&&s>=1) cout<<(m*t-s)/t*1.0<<endl;
    else cout<<"0";
	return 0;
 }