Platforms NEFU要崛起——第16场

                                                                                                               B. Platforms

                                                                   http://codeforces.com/problemset/problem/18/B

In one one-dimensional world there are n platforms. Platform with indexk (platforms are numbered from 1) is a segment with coordinates[(k - 1)m, (k - 1)m + l], andl < m. Grasshopper Bob starts to jump along the platforms from point0, with each jump he moves exactly d units right. Find out the coordinate of the point, where Bob will fall down. The grasshopper falls down, if he finds himself not on the platform, but if he finds himself on the edge of the platform, he doesn't fall down.

Input

The first input line contains 4 integer numbers n,d, m,l (1 ≤ n, d, m, l ≤ 10⁶, l < m) — respectively: amount of platforms, length of the grasshopper Bob's jump, and numbers m and l needed to find coordinates of the k-th platform:[(k - 1)m, (k - 1)m + l].

Output

Output the coordinates of the point, where the grosshopper will fall down. Don't forget that if Bob finds himself on the platform edge, he doesn't fall down.

Sample test(s)

Input

2 2 5 3

Output

4

Input

5 4 11 8

Output

20

和超级玛丽一样的题

代码：

 

 long long 于_int64的大小一样

#include<iostream>#include<cstdio>using namespace std;long long i,d,m,l,n,ans;long long i2,d2,m2,l2,n2,ans2;long long k;long long step;long long anss(long long n,long long d,long long m,long long l){    for (long long i=0;i<n;i++)    {        long long zuo=(i+1)*m;   //第i+1个台子左边         long long you=i*m+l;     //第i个台子右边         step=(you+d)/d;        if (step*d<zuo)            break;    }    return step;}int main(){    long long cas;       long long a1,a2;    long long c1,c2;           while(cin>>n>>d>>m>>l)        {                       c1=anss(n,d,m,l);                     cout<<c1*d<<endl;                             }                      return 0;}