codeforces 224 B. Number Busters

#include<cstdio>#include<iostream>#include<cstring>using namespace std;#define LL long longLL a,b,w,x,c;bool judge(LL t){if(b-x*t>=0)return c-t<=a;return c-t<=a-((x*t-b)/w+((x*t-b)%w!=0));}int main(){while(cin>>a>>b>>w>>x>>c){if(c<=a){cout<<0<<endl;break;}LL l=1;LL r=(LL)1<<60;while(l+3<r){LL mid=(l+r)>>1;if(judge(mid))r=mid;elsel=mid;}for(LL i=l;i<=r;i++)if(judge(i)){cout<<i<<endl;break;}}return 0;}