#include using namespace std; #define GET_MACRO(a, b, c, NAME, ...) NAME #define rep(...) GET_MACRO(__VA_ARGS__, rep3, rep2)(__VA_ARGS__) #define rep2(i, a) rep3 (i, 0, a) #define rep3(i, a, b) for (int i = (a); i < (b); i++) #define repr(...) GET_MACRO(__VA_ARGS__, repr3, repr2)(__VA_ARGS__) #define repr2(i, a) repr3 (i, 0, a) #define repr3(i, a, b) for (int i = (b) - 1; i >= (a); i--) template inline bool chmin(T1 &a, T2 b) { return b < a && (a = b, true); } template inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); } using ll = long long; int main() { int n, k; string s; cin >> n >> k >> s; ll buy = 0, num = 0, ans = 0; if (k >= n) { rep (i, n) { if (num == 0) buy++; else num--; num += s[i] - '0'; } ll x = num != 0 ? buy / num : k / n - 1; ans = (x + 1) * (buy + buy - x * num) / 2; num *= x; k %= n; } rep (i, k) { if (num == 0) ans++; else num--; num += s[i] - '0'; } cout << ans << endl; return 0; }