Ural_1017. Staircases(DP)

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int N = 501;

long long dp[N][N];

int main(){
    //freopen("data.in", "r", stdin);

    int n, i, j, k;
    long long ans;
    while(~scanf("%d", &n)){
        memset(dp, 0, sizeof(dp));
        for(i = 1; i <= n; i++){
            dp[i][i] = 1;
        }
        dp[3][2] = 1; dp[4][3] = 1;
        for(i = 5; i <= n; i++){
            for(j = 1; j < i; j++){
                for(k = 0; k < j; k++){
                    dp[i][j] += dp[i-j][k];
                }
            }
        }
        for(i = 1, ans = 0; i < n; i++){
            ans += dp[n][i];
        }
        printf("%lld
", ans);
    }
    return 0;
}