7 lines
228 B
C++
7 lines
228 B
C++
ll floor_sum(ll a, ll b, ll c, ll n)
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{
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if(a == 0) return b/c*n;
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if(a>=c or b>=c) return n*(n-1)/2 * (a/c) + n * (b/c) + floor_sum(a%c, b%c, c, n);
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ll m = (a*(n-1)+b)/c;
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return m*n - floor_sum(c, c-b+a-1, a, m);
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} |