Codeforces Round #234 (Div. 2), problem: (B) Inna and New Matrix of Candies solution

Codeforces Round #234 (Div. 2), problem: (B) Inna and New Matrix of Candies: http://codeforces.com/contest/400/problem/B

Codeforces Round #234 (Div. 2), problem: (B) Inna and New Matrix of Candies solution: http://ideone.com/dryQ7U

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

int main() {
    int n, m, c[1005], cnt, a, b, flag;
    flag=cnt=0;
    memset(c, 0, sizeof(c));
    char s[1005];
    scanf("%d%d", &n, &m);
    for(int j=0; j<n; j++) {
        a=0, b=1000;
        memset(s, 0, sizeof(s));
        scanf("%s\n", s);
        for(int i=0; i<m; i++) {
            if(s[i]=='G') a=i;
            else if(s[i]=='S') b=i;
        }
        if(b<a) {
                flag=1;
                break;
            }
            else {
                if(c[b-a]==0) cnt++;
                c[b-a]++;
            }
        if(flag==1) break;
    }
    if(flag==1) printf("-1\n");
    else printf("%d\n", cnt);
    return 0;
}