C++ :

#include <cstdio>
static long long a[1000005];
int main(){
    int n; if(scanf("%d", &n) != 1) return 0;
    for(int i=0;i<n;i++) scanf("%lld", &a[i]);
    int i = 0, j = n - 1, ans = 0;
    long long L = a[0], R = a[n-1];
    while(i < j){
        if(L == R){ i++; j--; if(i < j){ L = a[i]; R = a[j]; } else if(i == j){ L = R = a[i]; } }
        else if(L < R){ i++; L += a[i]; ans++; }
        else { j--; R += a[j]; ans++; }
    }
    printf("%d\n", ans);
    return 0;
}