C++ :

#include <cstdio>
typedef unsigned long long ull;
static ull F(ull x){ ull s = 0; while(x){ s += x; x /= 10; } return s; }
int main(){
    ull Y; if(scanf("%llu", &Y) != 1) return 0;
    ull lo = 1, hi = Y, ans = 0;
    while(lo <= hi){
        ull mid = lo + (hi - lo) / 2;
        ull v = F(mid);
        if(v == Y){ ans = mid; break; }
        if(v < Y) lo = mid + 1;
        else { if(mid == 0) break; hi = mid - 1; }
    }
    if(ans) printf("%llu\n", ans);
    else printf("-1\n");
    return 0;
}